SYSTEMATIC REVIEW ON THE EPIDEMOLOGY OF SILICOSIS


SYSTEMATIC REVIEW ON THE EPIDEMOLOGY OF SILICOSIS
INTRODUCTION
Silicosis (particularly the acute form) is characterized by shortness of breath, cough, fever, and cyanosis (bluish skin). It may often be misdiagnosed as pulmonary edema (fluid in the lungs), pneumonia, or tuberculosis
Silicosis (previously miner’s phthisis, grinder’s asthma, potter’s rot and other occupation-related names) is a form of occupational lung disease caused by inhalation of crystalline silica dust, and is marked by inflammation and scarring in the form of nodular lesions in the upper lobes of the lungs. It is a type of pneumoconiosis.
EPIDEMOLOGY OF SILICOSIS
Silicosis is a long-term lung disease caused by inhaling large amounts of crystalline silica dust, usually over many years. Silica is a substance naturally found in certain types of stone, rock, sand and clay. Working with these materials can create a very fine dust that can be easily inhaled. Once inside the lungs, the dust particles are attacked by the immune system. This causes inflammation (swelling) and gradually leads to areas of hardened and scarred lung tissue (fibrosis). Lung tissue that’s scarred in this way does not function properly.
People who work in the following industries are particularly at risk:
• stone masonry and stone cutting – especially with sandstone
• construction and demolition – because of exposure to concrete and
• paving materials
• pottery, ceramics and glass manufacturing
• mining and quarrying
• sand blasting
CLASSIFICATION
Classification of silicosis is made according to the disease’s severity (including radiographic pattern), onset, and rapidity of progression. These include:
• Chronic simple silicosis
Usually resulting from long-term exposure (10 years or more) to relatively low concentrations of silica dust and usually appearing 10–30 years after first exposure. This is the most common type of silicosis. Patients with this type of silicosis, especially early on, may not have obvious signs or symptoms of disease, but abnormalities may be detected by x-ray. Chronic cough and exertional dyspnea are common findings. Radiographically, chronic simple silicosis reveals a profusion of small (<10 mm in diameter) opacities, typically rounded, and predominating in the upper lung zones.

• Accelerated silicosis
Silicosis that develops 5–10 years after first exposure to higher concentrations of silica dust. Symptoms and x-ray findings are similar to chronic simple silicosis, but occur earlier and tend to progress more rapidly. Patients with accelerated silicosis are at greater risk for complicated disease, including progressive massive fibrosis (PMF).
• Complicated silicosis
Silicosis can become "complicated" by the development of severe scarring (progressive massive fibrosis, or also known as conglomerate silicosis), where the small nodules gradually become confluent, reaching a size of 1 cm or greater. PMF is associated with more severe symptoms and respiratory impairment than simple disease. Silicosis can also be complicated by other lung disease, such as tuberculosis, non-tuberculous mycobacterial infection, and fungal infection, certain autoimmune diseases, and lung cancer. Complicated silicosis is more common with accelerated silicosis than with the chronic variety.
• Acute silicosis
Silicosis that develops a few weeks to 5 years after exposure to high concentrations of respirable silica dust. This is also known as silicoproteinosis. Symptoms of acute silicosis include more rapid onset of severe disabling shortness of breath, cough, weakness, and weight loss, often leading to death. The x-ray usually reveals a diffuse alveolar filling with air bronchograms, described as a ground-glass appearance, and similar to pneumonia, pulmonary edema, alveolar hemorrhage, and alveolar cell lung cancer.
SIGNS AND SYMPTOMS
The symptoms of silicosis usually take many years to develop and you may not notice any problems until after you've stopped working with silica dust. The symptoms can also continue to get worse, even if you're no longer exposed.
In most cases, exposure for at least 10-20 years is required to cause the condition, although in a few cases it can develop after 5-10 years of exposure or, in rare cases, after only a few months of very heavy exposure.
WHO IS AT RISK FOR SILICOSIS?
Factory, mine, and masonry workers are at the greatest risk for silicosis because they deal with silica in their work. Silica is a highly common mineral found in sand, rock, and quartz. People who work in the following industries are at greatest risk:
• asphalt manufacturing
• concrete production
• crushing or drilling rock and concrete
• demolition work
• glass manufacturing
• masonry
• mining
• quarrying
• sandblasting
• tunneling
Workers and their employers must take steps to protect themselves from silica exposure.
MAIN SYMPTOMS
The main symptoms of silicosis are:
• a persistent cough
• persistent shortness of breath
• weakness and tiredness
If the condition continues to get worse, these symptoms may become more severe. Some people may eventually find simple activities such as walking or climbing stairs very difficult and may be largely confined to their house or bed. The condition can ultimately be fatal if the lungs stop working properly (respiratory failure) or serious complications develop (see below), but this is rare in the UK.
FURTHER PROBLEMS
Silicosis can also increase your risk of other serious and potentially life-threatening conditions, including:
• tuberculosis (TB) and other chest infections
• pulmonary hypertension
• heart failure
• arthritis
• kidney disease
• chronic obstructive pulmonary disease (COPD)
• lung cancer
The links above will take you to more information on these conditions, including their treatment.
HOW IS SILICOSIS DIAGNOSED?
People who suspect that they have silicosis should seek medical attention. The physician will ask questions about when or how the patient may have been exposed to silica. They can test lung function with pulmonary function tests.
A chest X-ray can test for scar tissue. On X-rays, silica scars appear as small, white spots.
A bronchoscopy may also be conducted. This procedure involves passing a thin, flexible tube down the throat. A camera attached to the tube allows the physician to view the lung tissue. Tissue and fluid samples can also be taken during a bronchoscopy.
HOW IS SILICOSIS TREATED?
Silicosis does not have a specific medical treatment. The aim of treatment is to reduce symptoms. Cough medicine can help with cough symptoms, while antibiotics can help to treat respiratory infections. Inhalers can be used to open up the airways. Some patients wear oxygen masks to increase the amount of oxygen in the blood.
Patients with silicosis should avoid further silica exposure. Because smoking damages lung tissue, quitting smoking can help. Because silicosis patients are at higher risk for tuberculosis (TB), they should be tested regularly for the condition. A physician can prescribe medications to treat TB. Patients with severe silicosis may require a lung transplant.
WHAT IS THE OUTLOOK FOR SILICOSIS?
Silicosis has become less common over time, thanks to increased work safety rules (MedlinePlus, 2013). However, silicosis can still occur. There is no cure for silicosis. After diagnosis, a person may live a few months to several years (American Lung Association, 2013). The prognosis depends on how severe the condition is. Intense lung scarring can develop in both accelerated and chronic silicosis. Scarring destroys healthy lung tissue, reducing the amount of oxygen the lungs can transmit to the blood.
PREVENTING SILICOSIS
Workers can wear special masks called respirators to keep from inhaling silica. These masks may be marked for “abrasive blasting” use. Silicosis can be prevented by avoiding prolonged exposure to silica dust. Water sprays and wet cutting methods reduce the risk for silica exposure. Work spaces should meet Occupational Safety and Health Administration (OSHA) standards. This includes proper ventilation. Employers can monitor air quality at worksites, to ensure that excess silica is not in the air. Employers must report all diagnosed incidents of silicosis.
Workers should eat, drink, and smoke away from silica dust. They should also wash their hands before doing any of these activities to reduce silica dust on the hands.
TREATING SILICOSIS
There's no cure for silicosis, as the lung damage cannot be reversed. Treatment aims to relieve symptoms and improve quality of life. The condition may continue to get worse, leading to further lung damage and serious disability, although this may happen very slowly over many years.
The following steps may limit the risk of complications:
• ensure you're not exposed to any more silica
• stop smoking (if you smoke)
• have regular test to check for TB, if advised by your doctor
• have the annual flu jab and the pneumococcal vaccination
You may be offered long-term oxygen therapy if you're having difficulty breathing and have low levels of oxygen in your blood. Bronchodilator medicines may also be prescribed to widen your airways and make breathing easier.
You'll be given a course of antibiotics if you develop a bacterial chest infection.
In very severe cases, a lung transplant may be an option, although there are strict health requirements to meet before this will be considered.

CONCLUSION
Silicosis is a lung disease caused by breathing in tiny bits of silica, a mineral that is part of sand, rock, and mineral ores such as quartz. It mostly affects workers exposed to silica dust in occupations such mining, glass manufacturing, and foundry work. Over time, exposure to silica particles causes scarring in the lungs, which can harm your ability to breathe.
Silicosis has been a human scourge since antiquity. In 1705, Ramazzini cited Diembrock's description of the lungs of stonecutters "in whom he found heaps of sand that in running the knife through the pulmonary vesicles he thought he was cutting through some sandy body." In 1870, Visconti introduced the term silicosis, derived from Latin silex, or flint. Although silicosis has been recognized for many centuries, its prevalence increased markedly with the introduction of mechanized mining. The prevalence has declined markedly in developed countries in recent decades because of effective industrial hygiene measures

REFERENCES

Jane A. Plant; Nick Voulvoulis; K. Vala Ragnarsdottir (13 March 2012). Pollutants, Human Health and the Environment: A Risk Based Approach. John Wiley & Sons. p. 273. ISBN 978-0-470-74261-7. Retrieved 24 August 2012.

Derived from Gr. πνεῦμα pneúm|a (lung) + buffer vowel -o- + κόνις kóni|s (dust) + Eng. scient. suff. -osis (like in asbestosis and silicosis, see ref. 10).
GBD 2013 Mortality and Causes of Death, Collaborators (17 December 2014). "Global, regional, and national age-sex specific all-cause and cause-specific mortality for 240 causes of death, 1990-2013: a systematic analysis for the Global Burden of Disease Study 2013.". Lancet. doi:10.1016/S0140-6736(14)61682-2. PMID 25530442.
United States Bureau of Mines, "Bulletin: Volumes 476-478", U.S. G.P.O., (1995), p 63.
Rosen G: The History of Miners' Diseases: A Medical and Social Interpretation. New York, Schuman, 1943, pp.459-476.

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